The design of distributed variable frequency pump system for several related applications

Abstract: As a new multi-point arrangement of circulating pump, distributed variable frequency pump system has the characteristics of saving electric energy and operating cost compared with single-point arrangement of circulating pump in traditional heating pipe network. This article describes in detail, and for the system design and application should pay attention to a number of issues put forward solutions, with a view to blaze new trails and improve together. Keywords: distributed variable frequency pump design and application of a distributed frequency conversion pump system principle In the traditional heat pipe network system, usually at the heat source or heat exchange station with a set of circulating pump, according to the network system flow And the most adverse loop resistance to choose the circulation pump flow, lift and the number of stations; pipe network system end users set manual control valve or self-flow control valve and other adjustment equipment to consume the user's remaining head pressure, within the system Each user's hydraulic balance; individual heat network due to changes in user heat load, capital pressure head is not enough, increase the water supply or backwater booster pump, but because of difficult to adjust, often upstream or downstream users adversely Impact. With the advent of new regulating devices and controls, digital control of the water pump is made possible, so that in principle it is possible to cancel the regulating equipment in the pipe network and replace it with a speed-adjustable water pump which is set at the appropriate node of the pipe network to Meet the subsequent hydraulic conditions. If you control the network node in the appropriate pressure drop, the point called the pressure control point, the choice of the main circulation pump, as long as the flow and heat to the pressure control point resistance can be, which can greatly reduce the circulation pump Of the head, making the main loop pump motor power many; economic control point after each user set the corresponding distribution variable frequency pump to become a distributed variable frequency pump system, so that the original valve throttling energy is no longer in vain to loss, because the pump can be frequency Speed ​​governor, the main circulating pump can greatly reduce power consumption, theoretically eliminating the need for conditioning equipment, while the heating system can work at a lower pressure level, the system more secure. China Urban Heating Association has also listed the research and development of distributed variable frequency pump system as "Tenth Five-Year Plan" of science and technology. Second, the design of distributed variable frequency pump system In the distributed variable frequency pump system, the design should be carried out according to the following steps: 1, pipe network system design, calculation of pipe network resistance. 2, the choice of pressure control points, different pressure control points corresponding to different equipment, initial investment and pipe network operating costs, technical and economic analysis should be selected. 3, choose the main circulation pump, the main circulation pump options to consider two aspects: A: flow requirements, should be able to provide the entire circulation network flow; B: lift requirements, should meet the heat source to the pressure control points between the pipe network resistance. 4, the choice of distribution pump, the main consideration to meet the resistance of the branch users and traffic. Third, the realization of distributed variable frequency pump system In accordance with the above ideas, Tangshan City Heating Corporation owned Longdong boiler room heating system has been transformed. In this paper, an example to illustrate the realization of distributed variable frequency pump system. 1, Longdong heating system consists of a 4 × 10t / h hot water boiler room and two for the station composition, the basic parameters are as follows: (1) heating construction area: Longnan Station: 181814.31m2 Long North Station: 139891.62m2 Total: 321705.93m2 (2) Equipment: Two main circulation pumps, one for each, ISR200-150-400, power N 90KW, flow Q 400m3 / h, lift H 50m water column. (3) Pipe network: 1-2 Pipe diameter DN300, groove length L = 500m 2-3 Pipe diameter DN250, groove length L = 536m 3-4 Pipe diameter DN250, groove length L = 650m According to the actual operation in recent years, Take the heat supply and return water temperature 105 ℃ / 65 ℃, the boiler room resistance loss of 10m water column, Longbei station resistance loss of 10m water column, Longnan station internal resistance loss of 5m water column, building thermal indicators take 55kcal / m2h. $$ Div $$ 2, by the above parameters, the calculation of the experimental transformation options are as follows: 1 boiler main loop pump replaced by H = 24m, Q = 480m3 / h, N = 45KW pump 2 Longnan station a water plus one Taiwan frequency conversion pump, H = 12.5m Q = 200m3 / h N = 15KW 3 Long North Station a water supply plus a variable frequency pump, H = 24m Q = 240m3 / h N = 22KW 4 Longnan, Pipe in parallel, and increase the original pipe valve. It should be pointed out that, due to the pump parameters can not exactly exactly meet the needs of the network, the equipment selection process has varying degrees of rounding. 3, in accordance with the boiler room main pump circulating pump room to provide 1-2 points and resistance loss, the station frequency conversion pump were to overcome the 2-3,2-4 and station resistance loss principle, the company this year, after the transformation of the East Long The heating system was commissioned. In the debugging process, we are in line with the premise of meeting the heating requirements, try to balance the temperature of a return water temperature of the two stations, and where possible, to maximize the distribution of variable frequency pump load and reduce the main circulating pump load , In order to save energy consumption as much as possible. Distributed inverter pump system put into operation, compared with the original single-point set circulation pump system, the measured current consumption is as follows: System Single-point circulation pump running current consumption of 130A; distributed variable frequency pump multi-point operation, the measured Data table is as follows: 4, distributed frequency conversion pump system put into operation before and after the main circulating pump outlet pressure decreased from 0.6Mpa to 0.39Mpa. 5, Analysis of several pump motor power factor difference is not between 0.78-0.81, if not consider the difference, energy saving rate (130-56-17.1-26.8) /130×100%=23.15% four, Conclusion Distributed variable frequency pump system is a new type of pump layout, compared with the traditional single point layout has the following advantages: 1, saving electricity; 2, the system as a whole lower the pressure level, the system more secure. Fifth, a few experience 1, the main circulation pump is generally arranged in the heat back to the water, the layout of the distribution pump (except the main circulation pump) should be at the thermal station water supply or as close to the economic control point of the water supply pipe. 2. It is necessary to recalculate the replenishment pressure at the replenishment point. Since it is difficult to arrange the distribution pump at the economic control point of the pipeline under normal circumstances, when the distribution pump is arranged in the station, when the branch line is longer, It is possible to cause drifting of the refill point. For such conditions, one way is to set the recharge point at the lowest point of the pipe network, or another way is still concentrated in the total heat backwater replenishment, water pressure increase the appropriate value. 3, the equipment selection, the main circulating pump technical parameters should be properly left margin. 4, the pressure control point at the differential pressure control: As the heating pipe network is far away from the signal transmission is not easy to achieve or higher cost, the calculated value converted to the main circulation pump import and export; or in the pressure control point back Water pipe installation pressure gauge, reference pressure gauge value to adjust the main circulation pump import and export of pressure. 5, In the variable frequency variable frequency pump system, because the technical parameter of the pump product is not continuous, it is impossible to meet the actual need, even if the frequency conversion adjustment can not just meet the requirements, the system of individual points of the valve adjustment is still necessary .